The best - and perhaps only - chance of victory for Ehud Barak, the One Israel candidate, is to persuade Yitzhak Mordechai, the former defence minister, to stand down and join forces with him.
One Israel, the new name for the Labour party, would offer Mr Mordechai, the candidate of the newly created Centre party, four or five ministerial posts in a new government, according to Israeli press reports. Mr Mordechai himself would become the deputy prime minister and defence minister.
Mr Netanyahu is a little behind Mr Barak in the polls, but the large number of voters who are declaring themselves to be "undecided" traditionally swing to the right.
Mr Mordechai, whom polls show will win some 17 per cent of the vote on 17 May, has failed to make the breakthrough that would enable him to survive until the second round of balloting. This takes place on 1 June if no candidate wins half the vote in the first round.
The Centre party leadership largely comprises politicians and members of the Israeli establishment who have quarrelled with Mr Netanyahu. According to the daily Maariv, its leaders - with the exception of Mr Mordechai - are reconciled to doing a deal before the election, in which they are likely to fare badly.
Mr Barak needs to win in the first round of the election, because as many as a quarter of the Israeli-Arab community may not turn out for voting on 1 June.
In the first round, Israeli-Arabs will be attracted to the polls because that is the Knesset election, in which they will be voting for their own parties as well as the prime minister.
One Israel, advised by American political consultants, has run a better- organised campaign in recent weeks. But this may make only a limited difference because voter loyalty in Israel is often determined by membership of ethnic or religious communities, such as the ultra-orthodox Jews or Russian immigrants. In this way, One Israel is at a disadvantage and, under its old name of Labour, has won only one election outright since 1973.
Even with Mr Mordechai supporting him, Mr Barak faces a close race. He needs Azmi Bishara, the Arab candidate for the prime minister's office, to throw his support behind him.
Mr Bishara currently has the support of 4 per cent of voters.
By contrast, Mr Netanyahu wants Benny Begin, the candidate of the far right, not to drop out in case he should set a precedent for Mr Mordechai also giving up.
If Mr Mordechai does decide to back Mr Barak, the partnership will probably be agreed only a week before the election, thus allowing Mr Mordechai to maximise his demand for jobs in a new government.
Amnon-Lipkin Shahak, the former Israeli chief of staff and a founder of the Centre party, would reportedly be made ambassador to Washington and also put in charge of negotiations with Syria.
The inability of the Centre party to make a breakthrough confirms the diagnosis of Yossi Beilin, one of the leaders of One Israel, that Israeli politics has few centrist or floating voters. This is because normal political differences are reinforced by the various religious, ethnic and class loyalties.
Such floating voters as do exist are enthusiastically pursued by all parties.
This is particularly true of the Russian immigrants, whose voting patterns are considered more fluid than those of other communities. Party leaders were yesterday courting Igor Ivanov, the Russian Foreign Minister, at the start of his visit to Israel.
Polls show that 91 per cent of Russian Jews in Israel want better relations with Russia.Reuse content